1. Field of the Invention
The invention generally relates to a vaccine and diagnostic for Lyme's disease. In particular, the invention provides a chimeric polyvalent recombinant protein comprising immunodominant epitopes of loop 5 and/or alpha helix 5 regions/domains of outer surface protein C (OspC) types associated with mammalian infections.
2. Background of the Invention
Lyme disease is the most common arthropod-borne disease in North America and Europe. It is caused by the spirochetes Borrelia burgdorferi, B. garinii and B. afzelii. Transmission to mammals occurs through the bite of infected Ixodes ticks [Burgdorfer et al, 1982, Benach et al., 1983]. Considerable morbidity is associated with Lyme disease and there are areas in the United States and Europe where up to 3% of the population is infected annually [Fahrer et al., 1991]. Infection results in a multi-systemic inflammatory disease with early stage symptoms that may include erythema migrans, low-grade fever, arthralgia, myalgia, and headache [Steere et al., 1977a]. Late stage clinical manifestations can be severe and may include in part, arthritis [Steere et al., 1977a; Eiffert et al., 1998; Steere et al., 2004], carditis [Asch et al., 1994; Nagi et al., 1996 Barthold et al., 1991] and neurological complications [Nachman and Pontrelli, 2003; Coyle and Schutzer 2002]. In addition, Lyme disease has significant socio-economic costs, manifested by reductions in outdoor recreational and social activities due to concerns about tick exposure.
Pharmacoeconomic studies indicate that a clear need exists for a Lyme disease vaccine, particularly in populations where the annual disease risk exceeds 1% [Meltzer et al., 1999; Shadick et al., 2001]. However, at the present time a vaccine is not commercially available. The first human Lyme disease vaccine was the OspA-based LYMErix (GlaxoSmithKline); however, its tenure was short and, citing a drop in sales, GSK voluntarily pulled it from the market in 2002. The decline in sales can be traced to concerns, real or perceived, of possible adverse effects including a chronic inflammatory arthritis that could theoretically develop in HLA-DR4-positive recipients [Kalish et al., 1993]. While new OspA-based vaccinogens are being developed to mitigate this potential complication [Koide et al., 2005; Willett et al., 2004], questions remain about the viability of an OspA-based vaccine. One concern is the frequency of boosts required to maintain long term protection. OspA is expressed in the tick midgut, is rapidly downregulated upon tick feeding, and is not expressed in mammals [Gilmore et al., 2001; Schwan et al., 1995]. The mechanism of action of OspA-based vaccines is to target spirochetes within the tick and prevent their transmission [de Silva et al., 1999]. Since transmission occurs within 48 hours of tick feeding, effective protection is dependent on high circulating titers of anti-OspA antibodies, necessitating frequent boosts. The inherent problems associated with OspA-based vaccines can be avoided by the use of antigens that are expressed at high levels during early infection and that elicit bactericidal antibody.
OspC has received considerable attention in Lyme disease vaccine development. It is a 22 kDa, surface exposed lipoprotein [Fuchs et al., 1992] encoded on a 26 kb circular plasmid that is universal among isolates of the B. burgdorferi sensu lato complex [Marconi et al., 1993; Sadziene et. al., 1993]. Its expression is induced upon tick feeding and is maintained during early mammalian infection [Schwan, 2004], and it is genetically stable during infection [Hodzic et al., 2000; Stevenson et al., 1994]. Anti-OspC antibodies have been demonstrated to protect against infection, but only against strains expressing OspC that is closely related in sequence to the vaccinogen [Gilmore et al., 1996; Bockenstedt et al., 1997; Gilmore and Mbow, 1999; Mathiesen et al., 1998; Scheiblhofer et al., 2003; Jobe et al., 2003; Rousselle et al., 1998; Wallich et al., 2001; Mbow et al., 1999; Probert et al., 1997; Brown et al., 2005; Probert and LeFebvre 1994]. Analyses of OspC sequences have delineated ˜21 OspC phyletic clusters or types that are differentiated by letter designation (A through U) [Seinost et al., 1999; Wang et al., 1999]. While sequence variation within a cluster is generally less than 2%, between OspC types it can be as high as 22% [Wang et al., 1999; Theisen et al., 1995; Brisson and Dykhuizen, 2004]. Such inter-type variation of epitopes most likely explains the limited range of protection afforded by vaccination with a single OspC type.
U.S. Pat. No. 6,248,562 (Jun. 19, 2001) to Dunn and Luft describes chimeric Borrelia proteins that consist of at least two polypeptides from corresponding and/or non-corresponding proteins from the same and/or different species of Borrelia. The chimeric polypeptides incorporated in the chimeric proteins are derived from any Borrelia protein from any strain of Borrelia and include OspA, OspB, OspC, OspD, p12, p39, p41, p66, and p93. The chimeric proteins can be used as immunodiagnostic reagents and as vaccine immunogens against Borrelia infection. However, there is no reference to loop 5 and alpha 5 epitopes present in OspC proteins.
U.S. Pat. Nos. 6,872,550 and 6,486,130 (Mar. 29, 2005, and Nov. 26, 2002, respectively) both to Livey, describe constructs for use a vaccines against Lyme disease which contain OspC antigens. However, there is no mention of the characterization of loop 5 and alpha 5 epitopes in these patents.
U.S. Pat. No. 7,008,625 (Mar. 7, 2006) to Dattwyler et al. discloses antigenic polypeptides of a variety of Borrelia strains and/or proteins within a single protein. The chimeric Borrelia proteins are made up of polypeptide fragments of the outer surface protein OspA and the outer surface protein OspC. These proteins can be effective against Lyme borreliosis as well as for immunodiagnostic reagents. However, there is no mention of the characterization of loop 5 and alpha 5 epitopes.
The publication “Recombinant Chimeric Borrelia Proteins for Diagnosis of Lyme Disease” (Maria J. C. Gomes-Solecki et al. 2000. J. Clin. Microbiol., 38: 2530-2535) is related to the two above-identified patents. The authors engineered recombinant chimeras, each containing portions of the key antigenic proteins of Borrelia burgdorferi, OspA, OspB, OspC, flagellin (Fla or p41), and a protein p93. The paper is directed to diagnosis, but describes applications to vaccinogens in the closing paragraph. The authors mention that better chimeras can be created with further study of the genetic variability of the important epitopes but do not mention the loop 5 and alpha 5 epitopes of OspC.
The prior art has thus-far failed to provide a vaccine that affords broad protection against multiple OspC types for use in the prevention and/or treatment of Lyme disease.